Field of the Invention
The present invention relates to the field of agricultural machinery and more particularly to that of the design, construction and employment of agricultural equipment intended to achieve the maneuvers and operations necessary for cultivation of plant production.
The subject of the invention is more particularly an agricultural hitch capable of achieving maneuvers automatically or semi-automatically, as well as a method for automated or semiautomated management and guidance of such maneuvers.
To accomplish the diverse agricultural tasks, it is usual to use agricultural machines powered and driven by tractors. These tractors are associated with carried tools or with semi-carried machines, or else with a certain number of towed machines.
Such tractor-machine(s) or tractor-tool(s) assembly is referred to generally and in the present case as agricultural hitch, or else motorized or mechanized agricultural hitch.
In particular, within the scope of the present invention, the objective is to apply a system and a method for management and guidance of repetitive maneuvers in the case of a tractor-tools assembly provided preferably with up to four hitched operational components (including the tractor). The half-turns at the end of the field constitute a preferred but non-limitative example of the maneuvers concerned by the present invention.
Description of the Related Art
The advent of mechanization in agriculture since the beginning of the 20th century led to the use of progressively more powerful, faster and larger hitches of tractor+machine(s). This phenomenon had as a consequence the need to progressively automate their functioning, at least partly, since exclusively human control was becoming increasingly haphazard. The field of agricultural machinery has therefore been the subject of numerous technological innovations relating to its automation, mainly by virtue of the use of electronic technologies, then of on-board electronic systems.
At present, by means of the system of the Müller Elektronik Company known as the “Headland Management System”, it is possible to record and to reproduce repetitive tasks (change of speed, deactivation or activation of the power take-off of the tractor, raising or lowering of the hitch, etc.) upon arrival at the end of the field. On the other hand, the half-turn maneuver is generally always managed by a driver. The driver follows an approximate path, while allowing for the width and turning radius of the agricultural machine (or of the hitch assembly). To the extent of repeated use of the same combination of tractor and hitched (or semi-carried) machine, the operator will be in better control of the maneuver and will empirically optimize the path being followed and the speed of the maneuver. As is known, the maneuvering times (especially at the end of the field) prolong the duration of a jobsite, since the machine is not productive during the half-turns.
U.S. Pat. Nos. 8,131,432B2 and 8,346,443B2 propose a method and a system for managing the half-turn of a vehicle by imposing limits on the work area. The tractor steers itself during the half-turns and thus controls the hitched machine.
The obligatory prerequisites for the solutions disclosed in these patents are:                to provide the limits of the parcel being worked,        to indicate the potential obstacles,        to define the dimensions and parameters of the tractor (normally already present in the control module of the tractor),        to define the dimensions and parameters of each hitched machine,        to geolocate the agricultural machines precisely by a system of GPS type.        
The teaching of these two documents corresponds to the steering control system known by the designation “iTEC Pro” (“Intelligent Total Equipment Control”—“Total intelligent control of the equipment”) of the John DEERE Company. This system is automated, but it is still necessary to indicate the direction in which the tractor must turn (to the right or left).
It is also known how to use automatic management of half-turns on combine harvesters. On such a motor vehicle, the working implements used (such as the cutter bar, for example) are directly mounted on the motor vehicle and are easily controllable in position. The current systems of this type (for example that known by the designation “GPS PILOT FLEX”) necessitate the use of geolocating systems in order to function.
Consequently, according to the existing prior art, the half-turn at the end of the field can be accomplished according to the following types of methods:
1. Manual guidance (most widely used method). The driver estimates the usable space “by eye” and tries “to fit” the path of the tractor-tools assembly into this space.
2. Autoguidance by learning. This guidance system records a typical path followed by the operator and repeats this path.
3. Automated half-turn, assisted by a geolocating device of GPS type (the user is required to enter the geometry of the tractor-tools assembly and the turning direction).
Thus it results from the foregoing that automated guidance of agricultural tools during half-turns is a known method, but only in certain configurations, such as presented, for example, in: U.S. Pat. No. 8,346,443B2, U.S. Pat. No. 8,577,558B2, EP 2659759A1, US 2013/0289883A1, US 2012/0185139A1, US 2005/0015189A1.
In all of these known solutions, the automatic guidance of the maneuvers is steered by the tractor (which if necessary integrates an additional electronic unit integrated in it), and it necessarily uses an external geolocating system.
Both manual operation and the known automated solutions have, in their practical use, inconveniences and limitations that must be overcome.
Thus manual operation of assemblies containing towed tools constitutes a difficult and complex task, requiring that the driver be attentive and vigilant at all times. The expansion of the working width (for example in the case of harvesters, seeders and sprayers) and the increase in the number of hauled elements as well as the increase in working speed in the field are making the operation of such equipment progressively more complicated and accident-prone. The most sensitive aspect concerns in particular maneuvers at the end of the field, such as half-turns. As an example, the drivers or operators are forced to reduce the forward speed and to counter-steer in order to compensate for the poor maneuverability of large machines, all while fitting the mobile assembly into a reduced maneuvering zone at the end of the field (headland). Studies made in the field show that close to 20% of the working time may be lost during maneuvers at the end of the field. In addition, the soil of the headland zone is more compacted because of the maneuvers taking place there, and this reduces the harvest yield. The width of headlands must therefore be reduced to the minimum, but this complicates the strategy for establishing maneuvering paths. It is difficult for a human operator to take all of these parameters into account in order to determine a path at the moment when he is executing the maneuver.
The known automated solutions, based on on-board intelligence at the level of the tractor, also have their negative aspects.
Thus, when it is the tractor that manages the half-turn of a hitched tractor-tools assembly, the user must indicate a large number of data pertaining to the hitched (or semi-carried) elements so that the tractor will be capable of executing the half-turn in automatic mode. Effectively, it is the hitched (or semi-carried) equipment that embodies the most design variants and adjustment parameters for achieving the desired technical operations. A data-acquisition operation must therefore be implemented upon each change of machine and for each new machine, which is tedious, a source of errors and time-consuming.
In the case of takeover of control by the tractor, the current systems necessitate geolocation of the tractor and in general of the towed elements also. Such equipment is costly and may undergo drifts, especially in the case of large parcels (due to the imperfect sphericity of the Earth). In addition, the procedure for obtaining paths in the case of the known solutions is not optimized: the established path is initially that of the tractor, whereas the important factor for the agricultural operation to be executed is the positioning and the path of the towed or semi-carried working tools, which are generally the broadest elements (and therefore the least maneuverable).
Finally, in these known automatic systems, it is the path of the tractor that is controlled, as well as the absence of contact between the tractor and the first hitched machine, by the control of the distance between them. Thus, in the case of half-turns, the positioning of the machines or tools at the exit and entrance of the working zone, which constitute the most important parameters, is not controlled and even more so is not guaranteed.